1. Field of the Invention
The present invention relates, in general, to instrumentation for and a method of sizing a distal femur and guiding a bone resection tool to make anterior and distal femoral resections.
2. Information Disclosure Statement
In order to implant a distal femoral prosthesis on a distal femur, certain substantially "standard" steps are taken. One of the initial steps is to accurately size the distal femur to assist the surgeon in selecting the proper prosthesis size. Other steps include a plurality of resections or cuts made to the end of the distal femur to prepare the end of the distal femur to receive the prosthesis. These resections or cuts may include: (1) a distal femoral resection to remove a portion of the distal surface or end of the distal femur substantially equal to the thickness to be replaced by the distal condyle of the prosthesis unless special ligament problems dictate otherwise, etc.; (2) an anterior femoral resection to remove a portion of the anterior aspect of the distal femur; (3) an anterior bevel resection or resections to remove an angular portion of the distal femur between the distal femoral resection and the anterior femoral resection; (4) a posterior resection or resections to remove a portion of the posterior surface of the distal femur; (5) a posterior bevel resection or resections to remove an angular portion of the distal femur between the distal femoral resection and the posterior resection; (6) a patellar track groove cut to create or enhance the shallow groove in the femoral patellar groove to accommodate a recessed patellar track of a femoral prosthesis; and (7) a posterior stabilized cut or cuts to create a cavity for receiving the housing of a posterior stabilized femoral prosthesis.
Surgical techniques and instrumentation for preparing a distal femur to receive a distal implant prosthesis are disclosed in the document, Total Condylar & Posterior Stabilized Surgical Technique, ORTHOLOC.RTM. ADVANTIM.TM., Wright Medical Technology, Inc. (1993). As disclosed therein, multiple steps are taken to prepare a distal femur to receive a distal femoral prosthesis. In general, the steps start with preoperative planning to estimate the size of the prosthesis needed by comparing a lateral radiograph of the distal femur with an implant template. The template size that most closely matches the profile of the distal femur on the anterior and posterior aspect is normally chosen. If full length extremity films are available, the appropriate valgus angle may be estimated by the angle formed between the anatomical axis (the longitudinal axis of the femoral shaft) and the mechanical axis (a line extending between the centers of the femoral head, the knee joint, and the ankle joint). The knee joint can then be exposed and a femoral sizing caliper used to confirm the size estimate made during preoperative templating as disclosed at page 5 of the Total Condylar & Posterior Stabilized Surgical Technique, ORTHOLOC.RTM. ADVANTIM.TM. publication. The femoral sizing caliper is extended and placed flush over the distal femur with the posterior aspect of the caliper positioned against the posterior condyles, with a moveable anterior gauge positioned against the anterior cortex, and with a feeler gauge rod positioned parallel to the longitudinal axis of the femoral shaft with its indicator point resting directly on bone that is clear of any tissue. The proper implant size can then be read from the face of the caliper. A distal femoral cut guide is positioned on the distal femur and a distal femoral resection is made using an oscillating saw as disclosed at pages 7-9 of the Total Condylar & Posterior Stabilized Surgical Technique, ORTHOLOC.RTM. ADVANTIM.TM. publication. The distal femoral cut guide is then removed and an anterior/posterior (ALP) bevel cut guide is seated flush against the distal femoral cut using bone clamps and/or nails, Steinmann pins, etc., and an anterior condyle or flange resection is made using a wide saw blade and the A/P bevel cut guide as disclosed at pages 11-12 of the Total Condylar & Posterior Stabilized Surgical Technique, ORTHOLOC.RTM. ADVANTIM.TM. publication. A medial anterior bevel resection is made using a wide saw blade and the A/P bevel cut guide, a lateral anterior bevel resection is made using the a saw blade and the A/P bevel cut guide, a medial posterior bevel resection is made using a narrow saw blade and the A/P bevel cut guide, a lateral posterior bevel resection is made using the narrow saw blade and the A/P bevel cut guide, a medial posterior condyle resection is made using the narrow saw blade and the A/P bevel cut guide, and a lateral posterior condyle resection is made using the narrow saw blade and the A/P bevel cut guide as disclosed at pages 11-12 of the Total Condylar & Posterior Stabilized Surgical Technique, ORTHOLOC.RTM. ADVANTIM.TM. publication. The A/P bevel cut guide is then removed and a patellar track positioner is fixed to the distal femur to guide a cutting tool, such as a powered patellar track burr, to cut or resect a patellar track groove in the distal femur to accommodate the recessed patellar track of the final femoral implant prosthesis as disclosed at page 18 of the Total Condylar & Posterior Stabilized Surgical Technique, ORTHOLOC.RTM. ADVANTIM.TM. publication. If it is desired to implant a posterior stabilized femoral prosthesis, a posterior stabilized endmill guide is secured to the patellar track positioner, and a posterior stabilized endmill cutter is then used with the posterior stabilized endmill guide to cut or resect a posterior stabilized cut in the distal femur to accommodate the posterior stabilized housing as disclosed at pages 42-43 of the Total Condylar & Posterior Stabilized Surgical Technique, ORTHOLOC.RTM. ADVANTIM.TM. publication. A housing punch may be used with the posterior stabilized endmill guide to remove any remaining bone posterior to the endmill cut. Alternatively, a rongeur or saw may also be used after the posterior stabilized endmill guide is removed.
Dunn et at., U.S. Pat. No. 4,759,350, issued Jul. 26, 1988, discloses a system of instruments for preparing a distal femur to receive a distal implant prosthesis. The Dunn et al. system includes a distal femoral cutting guide 65 shown in FIGS. 7 and 8 thereof that is mounted to an alignment guide 40 after an anterior femoral cutting guide 55 has been used to cut through the anterior condyles 51 to create a flattened area on the distal femur, and after the anterior femoral cutting guide 55 has been removed from the alignment guide 40.
Sutherland, U.S. Pat. No. 5,129,909, issued Jul. 14, 1992, discloses an apparatus and method for making precise bone cuts in a distal femur. The Sutherland apparatus and method is used after a femoral cutting block (not shown) has first been used to guide an oscillating saw to accomplish a distal femoral resection by removal or resection of the distal condyles to provide planar surfaces on the distal femoral.
None of these patents or references disclose or suggest the present invention. That is, none of these patents or references disclose or suggest instrumentation or a method for sizing the end of a distal femur and then guiding a bone resection tool to make anterior and/or distal femoral resections. More specifically, none of these patents or references disclose or suggest instrumentation for or a method of mounting an instrument body construct including an instrument body and a valgus module on the distal end of an intramedullary rod with a portion of the construct resting against the unresected distal aspect of a distal femur and with another portion of the construct resting snugly against the posterior aspect of the distal femur; mounting an anterior feeler gauge on the construct and adjusting the assembly so the anterior feeler gauge contacts a portion of the anterior aspect of the end of the distal femur to thereby measure the anterior-posterior size of the distal femur; mounting a resection guide on the construct; and then using the resection guide to guide a bone resection tool to make anterior and/or distal femoral resections.